Various viruses such as microorganisms included in sewage are generally sterilized before the sewage in a sewage processing plant is discharged into a river. The sterilization methods include a chlorine sterilization method, an ultraviolet ray sterilization method and an ozone sterilization method. The ultraviolet ray sterilization method is directed to inactivating microorganisms by destroying the structures of microorganisms by radiating ultraviolet rays. The sterilization can be performed by radiating only a few seconds at a proper radiation level, so it is assumed as an environment friendly method.
The ultraviolet ray sterilizer installed at a waterway or a water pipe of a conventional sewage process plant is characterized in that a plurality of ultraviolet ray lamps are horizontally or vertically installed with respect to the direction of water flow at regular intervals in the upward, downward, leftward and rightward directions. So, the harmful microorganism in the treatment water is sterilized and removed by radiating ultraviolet rays to the treatment water flowing near the ultraviolet ray lamps.
The conventional ultraviolet ray sterilizer is characterized in that a cylindrical ultraviolet ray lamp of a diameter of 15-30 mm that is protected in a crystal tube and is installed underwater, so the ultraviolet rays are radiated from the ultraviolet ray lamps, thus sterilizing the microorganisms in the region where the ultraviolet rays are transmitted. However, there is a problem in that the ultraviolet rays don't reach the regions where the ultraviolet rays don't transmit, thus making non-sterilization zones where viruses are not sterilized. So as to resolve the above mentioned problems, as shown in FIG. 1a, Korean patent registration number 0924392 discloses an “ULTRAVIOLET STERILIZATION AND PURIFICATION APPARATUS EXCLUDING DEAD ZONE OF ULTRAVIOLET RADIATION”. The sterilization apparatus as shown in FIG. 1a is characterized in that a crystal tube 2 into which is inserted an ultraviolet ray lamp 3 that is positioned in the cylindrical tube 1, thus removing the ultraviolet ray radiation dead zones where the sterilization is not performed due to ultraviolet rays that don't reach. However, the above-mentioned invention is constituted in a structure in which each ultraviolet ray lamp 3 is inserted into the cylindrical tube 1 in a longitudinal direction, so the construction is complicated. When it is necessary to exchange and clean each ultraviolet ray lamp 3, it is necessary to attach or detach one by one the ultraviolet ray lamps 3. Since it is necessary to be connected to a water pipe when in use, the inlet and outlet 4a and 4b should be twisted at an angle of 90° or 180° with respect to the existing water pipe direction when connecting to the water pipe. In addition, since the above mentioned invention is characterized in that the ultraviolet ray lamp 3 being inserted in a longitudinal direction of the cylindrical tube 1, it cannot be installed at the open type water way. FIG. 1b is a view showing a structure in which a crystal tube 2′ is inserted into the cylindrical tube 1′ in the longitudinal direction of the tube 1′ like in the invention as shown in FIG. 1a. For this reason, the inlet and output 4a and 4b of the invention as shown in FIG. 1b can be twisted at an angle of 90° and can be connected to the water pipe; however it cannot be installed in a water way the upper side of which is open.
In addition, as a technology which can be installed in an open type water way so as to remove the non-sterilization regions, as shown in FIG. 2, Korean utility model registration number 0295112 is characterized in that a reflection member 1″ the surface of which is mirrored that is installed between the lamp 3″ and the lamp, thus allowing the ultraviolet rays from the ultraviolet ray lamps to reach the non-sterilization regions. The above mentioned invention can be installed in an open water way and can partially remove the non-sterilization region where the ultraviolet rays don't reach, with the aid of the mirrored reflection member 1″; however the space between the ultraviolet ray lamps 3″ and the apex portions of the diamond shape still form non-sterilization regions. Since the structure for the purpose of removing the dead zones of the ultraviolet ray radiations does not form a concentric circle in the diamond shape, the pressure loss in the flow way increases, and it is impossible to install the washing apparatus for the purpose of removing the contaminants such as moss and organic substances stuck to the surface of the crystal tube, so the contaminants come to block the ultraviolet rays, thus reducing sterilization power. The open type ultraviolet ray sterilizer is basically configured for the sake of the sterilization of the water in the sewage treatment plant in which the crystal tube is contaminated by moss or the like, so the above invention cannot be actually applied as an ultraviolet ray sterilizer.
In addition to the harmful microorganisms, micro organic substances or floating substances are contained underwater in the sewage treatment plant which flows in the ultraviolet ray radiation regions. Such substances might stick to the outer surface of the crystal tube protecting the ultraviolet ray lamp, thus forming an organic film thereon, so it comes to block the ultraviolet rays which radiate into the water by way of the crystal tubes by forming the organic film, so sterilization power might be reduced or such substances come to float around the crystal tube, thus narrowing the range of the ultraviolet ray radiation region. When the turbidity increases due to the floating substances contained in the treatment water, the ultraviolet rays radiated from the ultraviolet ray lamp don't reach far, and the organic substances might accumulate on the surface of the crystal tube thus forming a film thereon, so the radiation of the ultraviolet rays is greatly decreased from the ultraviolet ray lamps, and the sterilization of the microorganism is not fully performed.
In order to overcome the above mentioned problems in the conventional art, there is provided a machine type crystal tube washing apparatus in which a ring shaped wiper surrounding the outer side of the crystal tube configured to protect the ultraviolet ray lamp underwater is installed, and the wiper moves leftward and right ward in the longitudinal direction along the outer surface of the crystal tube thus washing the surface of the crystal tube. For an example, there is Korean patent registration number 0453740. The above mentioned machine type crystal tube washing apparatus adapts an air and hydraulic cylinder method in which a metallic wire brush matching with the outer diameter of the crystal tube or a Teflon material sleeve which makes abrasion against the contaminants stuck to the outer surface of the crystal tube so as to clean the outer surface of the crystal tube in the underwater way type ultraviolet ray sterilizer or adapts a method for removing contaminants by reciprocating the sleeve by means of the rotation of the shaft. The above mentioned methods have the problems in that as the crystal tube washing apparatus is used for a long time, the sleeves configured to remove the contaminants from the crystal tube become worn out or loosened or the washing efficiency of the crystal tube worsens due to the frequent errors of the parts belonging to the washing apparatus, so the contaminants might be stuck to the crystal tube, so the amount of the ultraviolet rays transmitting into the water by way of the crystal tube is decreased, thus still resulting in a lowered and weakened sterilization power.
There is an attempt to coat titanium dioxide on the crystal tube so as to actually adapt the automatic washing function for the sake of a crystal tube contamination prevention of the ultraviolet ray sterilizer, the automatic washing function originally configured to wash the contaminants from the outer wall of the building with the aid of the photolysis operation and to keep clean the outer wall of the same by using a super hydrophilicity and contaminant degradation power of the photo catalyst so as to overcome the problems encountered in the machine type crystal tube washing apparatus. Korean patent publication number 2004-0056940 discloses an ultraviolet ray sterilizer providing a sterilization and contaminant degradation operation by mixing the particle type photo catalyst with the binder and coating it on the outer surface of the crystal tube.
When the titanium dioxide is coated on the crystal tube of the ultraviolet ray sterilizer, the titanium dioxide absorbs ultraviolet rays and helps perform a photo catalyst reaction, so the ultraviolet rays from the ultraviolet ray lamps can be absorbed by the titanium dioxide coated on the outer surface of the crystal tube, thus producing OH-radicals. Therefore, the contaminants are prevented from sticking to the crystal tube with the aid of the photo crystal reaction which provides sterilization operation to the contaminants, while making sure that the microorganism of the surface of the crystal tube can be sterilized. In this case, most of the ultraviolet rays from the ultraviolet ray lamps are blocked by the titanium dioxide coated on the crystal tube, in other words, they are not radiated into the water, it is impossible to sterilize the microorganism with the aid of the ultraviolet rays. In this case the sterilization can be performed only by means of the OH-radicals produced on the surface of the titanium dioxide coated on the outer surface of the crystal tube, so the regions except for the surface of the titanium dioxide are not sterilized, so the sterilization is not properly performed, and it cannot be used as an ultraviolet ray sterilizer.
In particular, as disclosed in Korean publication number 2004-0056940, when the powder type photo catalyst is mixed with the inorganic binder and is heat-treated at about 100° and is coated, the inorganic binder not having a photo catalyst activation is inevitably coated on the surface of the photo catalyst while the powder type titanium dioxide photo catalyst is mixed with the silane inorganic binder and is coated on the surface of the crystal tube, so the contacts with the ultraviolet rays are blocked, not showing any activation. In addition, the binder configured to fix the photo catalyst is prevented from contacting with the contaminants or microorganism, so the photo catalyst reaction is reduced.
When the photo catalyst powder is coated, since it is impossible to obtain a photo catalyst coating layer smaller than the size of the photo catalyst particle, it is impossible to perform the ultraviolet ray sterilization operations while providing a contamination prevention function of the crystal tube by adjusting the thickness of the photo catalyst coating layer and the amount of the ultraviolet ray transmission due to the characteristics of the titanium dioxide having a good ultraviolet ray shielding effect. When using for long periods of time underwater, the coating layer becomes peeled off underwater.
For the above mentioned reasons, the crystal tube of the ultraviolet ray sterilizer should elastically insulate the ultraviolet ray lamps installed in the underwater and should transfer the ultraviolet rays from the ultraviolet ray lamps into the water without any losses, so when coating the titanium dioxide on the crystal tube, the titanium dioxide having a good ultraviolet ray blocking effect is characterized in that most of the ultraviolet rays from the ultraviolet ray lamps are blocked by the photo catalyst. For this reason, it has been prohibited from being coated on the outer surface of the crystal tube adapted in the ultraviolet ray sterilizer.
Consequently, the ultraviolet ray sterilizer used by coating a photo catalyst on the crystal tube like in Korean patent publication number 2004-0056940 is characterized in that thanks to the characteristics of the ultraviolet ray sterilizer configured to sterilize the microorganism underwater by means of the ultraviolet rays radiated into the water by way of the crystal tube as the ultraviolet rays pass one time through the microorganism, the sterilization operation is limitedly performed on the surface of the photo catalyst coated on the outer surface of the crystal tube, so the sterilization effects are greatly lowered, thus resulting in a lowered sterilization efficiency. Though it can provide a crystal tube contamination prevention function, the actual use of the same is not currently performed.
Meanwhile, there is provided an ultraviolet ray sterilizer characterized in that a photo catalyst is coated on a coil type metallic spring carrier, not coating on a crystal tube, and it is filled around the crystal tube into which is inserted the ultraviolet ray lamp. The above-mentioned sterilizer for the sake of drinking water in a temporal piped water facility is awarded a good product certificate (number 2009059) from the public procurement service of Korea.
For the above-mentioned reasons, in the coating method for a crystal tube contamination prevention, it is urgently needed to develop a new photo catalyst coating technology featuring a blocking ratio of the ultraviolet rays that can be controlled by adjusting the thickness of the photo catalyst thin film coated on the outer surface of the crystal tube and coated film that is not peeled off even though it is used for a long time underwater so as to provide a transmission function of ultraviolet rays and a contamination prevention function on the outer surface of the crystal tube so that the ultraviolet ray sterilizer can have a desired sterilization function with the aid of the ultraviolet rays.